Development of fast testing procedures for determining the leachability of soils contaminated by heavy metals

Abstract

In the Netherlands, the use of mildly contaminated soils, both treated and untreated, in civil and public works is regulated by the Dutch Act for Building Materials (“Bouwstoffenbesluit”) [ 1 ]. By law, the leachability of inorganic contaminants and heavy metals, as determined by the column test (NEN 7343), is not permitted to exceed certain values. Drawbacks of the prescribed test procedure are the relatively high costs and the long time needed for testing. The latter adds to the logistics of soil handling and utilization. Therefore, faster and less costly testing procedures for determining the leachability of soils are required. Over the last 3 years, an extensive study has been performed on the leachability of Cd, Cu, Zn, Pb, Hg, Ni, As and cyanide in treated and untreated soils and some dredged sediments. In this study and earlier studies 230 samples of untreated and treated soils and dredged sediments were analysed for specific soil parameters, contaminant contents and leachability. The analytical data were accumulated, statistically interpreted and evaluated. Some of these soil samples were selected for geochemical speciation modelling [ 2 ], some other soil samples were selected for studies on the effects of thermal treatment on leaching behaviour [ 3 ]; the results are reported in separate papers in these conference proceedings. The study resulted in: (1) a deeper level of understanding of the chemical and physical processes governing the leachability of contaminants from (re-usable) soils; (2) the description of a less time-consuming procedure for assessing the leachability of contaminants from (re-usable) soils. The latter result can reduce the need for temporary storage and consequently can lower the handling and logistic costs considerably.